LIVERMORE — Amid the lush green hills off Tesla Road, near the San Joaquin County line, is a serene area of sycamores and buckeyes with a secret past, and a controversial plan for its future.

It once was home to the bustling coal-mining town of Tesla, its dusty roads filled with horse carriages. Now California is looking at a proposal to expand the off-road vehicle area next door into portions of the 3,500-acre Tesla parcel, which State Parks officials say can be done while respecting the area’s history.

The idea has sparked a vigorous debate. On one side are off-roaders whose dirt bikes and ATVs jam the adjacent Carnegie State Vehicular Recreation Area, one of just eight state off-road vehicle parks, and the only one between Hollister and Sacramento.

Riders are “champing at the bit” for more opportunities, said Randy Caldera, superintendent at Carnegie. “I’d love to give these guys somewhere to go.”

On the other side are those who say the noisy vehicles — kicking up dirt over a ridge and out of earshot of the near-pristine Tesla — are plenty close enough.

Visiting Tesla is “almost a spiritual type of experience,” said Celeste Garamendi, sister of U.S. Rep. John Garamendi, D-Walnut Grove, whose family cattle ranch is nearby. “Every inch of it has something unique about it that would designate it as a historical and cultural park.”

Garamendi helped found Friends of Tesla Park to build support for making the land into a low-impact recreational park and natural preserve, free of motorized vehicles.

In their heyday, Tesla and nearby Carnegie boasted about 2,000 residents; both towns were abandoned by the 1920s. Native American ceremonial sites have been found on the Tesla grounds, alongside mine remnants and home foundations.

The area has been closed since the state bought it in 1998 with $7.4 million from the Off-Highway Vehicle Trust Fund, with the intent of expanding Carnegie’s 1,500 acres.

Carnegie visitors topped at 132,000 in 2006, but declined to about 80,000 users in 2011. For comparison, Mt. Diablo State Park had 250,000 visitors that year.

State Parks Off-Highway Vehicle division officials blame the economy for the drop, but say recent numbers are up and they expect a return to peak levels.

About 1,000 riders visit Carnegie on weekends, with cars lining up along Corral Hollow Road to get in, Caldera said.

At $5 per entry vehicle and $10 to camp overnight, Carnegie is a low-cost option for family fun, said Diana Mead, the Northern California director for the California Off-Road Vehicle Association. She visits Carnegie to ride quad ATVs and watch her son, a professional dirt bike hill-climber.

“It’s the only public (off-highway vehicle) opportunity in the Bay Area,” she said.

But, she said, Carnegie is limited for four-wheel vehicles such as dune buggies and sandrails — lightweight vehicles for navigating sand and dirt. Expansion would make it more family friendly and give riders a place to go where they can be regulated, she said.

“I’m excited about the state being able to manage it,” Mead said. “We’re going to allow access so people can enjoy it.”

Though Carnegie is noted for extreme riding, it’s common to see families. Todd Stanley, 16, of Manteca, has ridden dirt bikes there since age 3. Other off-road parks “don’t really compare,” he said.

“It’s my favorite place to ride in the state,” said his dad, Chris Stanley. “It’s cheap, easy and fast.”

The Friends of Tesla Park alliance against Carnegie’s expansion includes the Livermore Heritage Guild, the California Native Plant Society’s East Bay chapter and the Tri-Valley Group of the Sierra Club.

They want a visitor center built at Tesla — about two miles from the farthest Carnegie dirt trails — with low-impact hiking and biking trails and docent-led walks.

They say fencing off areas won’t guarantee preservation and that vehicle noise will drive away visitors seeking a refuge.

Jeff Kaskey, president of the Livermore Heritage Guild, said little remains of Tesla, but the site is a “visceral experience” of a significant bygone era.

“It’s another piece of our history that we lose,” he said. “Tesla represents how we got to where we are.”

According to State Parks’ Bob Williamson, district superintendent for state vehicular recreation areas in Northern California, some of the land has historical significance but not all of it. As part of its expansion plan, the state is mapping historic sites and works with tribes to identify sensitive areas.

“We would certainly have those concerns addressed in the draft (environmental report),” Williamson said.

After a preliminary general plan is released in the summer, State Parks will hold public hearings, followed by a draft plan and another round of public input. A revised general plan could be ready for a vote by the off-highway vehicle division commission — the final decision-making body for certification — by year’s end.

Meanwhile, Garamendi said she’ll continue working with elected officials to limit Carnegie’s growth.

“Tesla,” she said, “is not an appropriate or suitable place to expand.”

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